Anthony Alvarez, 26, was suspected of stabbing a city Water Department worker to death in April, according to The San Francisco Chronicle. The attacker was wounded during a struggle and police found a three-block-long blood trail but the Chronicle says a DNA sample still hadn't been analyzed by the police lab as of Monday.

It only takes about a week for DNA results to be obtained from blood samples, officials say. However, the San Francisco lab's backlog is so bad, it could take months for investigators to get the evidence. Blood from the city worker homicide could have been compared to a sample Alvarez provided after a 2008 drug arrest, perhaps changing the outcome of the Sacramento standoff.